Equake mode should be frame-local rather than buffer-local#19

Since the `equake-mode` minor mode is set buffer-locally, two undesirable UX issues arise: - when opening a non-equake buffer in an equake frame, the tab list disappears (which is rather inconvenient) - when opening an equake buffer in a non-equake frame, the tab list appears Perhaps `equake-mode` can be set frame-locally. Or else, some workaround can be put in place to toggle the buffer-local `equake-mode` based on frame properties/name. Possibly utilising native tabs in Emacs (see https://gitlab.com/emacsomancer/equake/-/issues/14 ) could also be helpful in resolving this issue.